1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image forming apparatus such as a copier, printer, or facsimile machine, or combinations thereof “combined apparatus”, hereafter) having the sheet processing apparatus mounted in a mainbody of its own and for performing image forming.
2. Related Background Art
FIG. 13 shows a conventional sheet processing apparatus that performs a processes, such as folding process and a binding process, of a sheet on which an image is formed in an image forming apparatus (see Japanese Unexamined Patent Application Publication No. 2003-095519). As shown in the drawing figure, a sheet processing apparatus 503 is disposed on the side of a main body of an image forming apparatus 501. The image forming apparatus 501, shown in FIG. 13, has an image reader 502 above the image forming apparatus 501.
In the sheet processing apparatus 503, sheets each having an image formed in the main body of the image forming apparatus 501 on a single side or double sides are serially taken in, and various processes are appropriately performed corresponding to setting. The processes include, for example, a folding process for folding a set of sheets (or, a “sheet set”, hereafter) in two (“bi-folding”, hereafter), and a single-side binding process for performing binding of edge of the sheet. For example, in the folding process for performing bi-folding of a set of sheets, the sheets serially taken in, as described above, are serially stacked on a saddle tray 504 formed substantially straight with a steep tilt and disposed substantially in a vertical direction, and are aligned into a set of the sheets. The sheet set is stapled using a stapling unit 505 substantially along the center portion of the sheet set. Then, the saddle tray 504 is moved to a binding portion (binding position) of the sheet set at the position of a folding device shown at numerals 506 and 507. The sheet set is folded there by the folding device shown at numerals 506, 507 in two, and concurrently, ejected onto a stack tray 508.
In the conventional sheet processing apparatus 503 described above, the folding device, which double-folds a sheet set, is configured of components, such as a folding roller pair 506 (i.e. a pair of rollers) and a push-out mechanism formed of a pushing plate 507 and the like. The binding position of the sheet set is pushed by the pushing plate 507, and the sheet set is folded to a nip of the folding roller pair 506. Then, the folded sheet set is pinched and carried by the folding roller pair 506, and concurrently, is bi-folded. Thereby, the sheet set is folded by the stapling unit 505 along the binding position in the center of sheet set, and is ejected in a book-bound form to the stack tray 508.
When performing the single-side binding process for edges of the sheet set, the conventional sheet processing apparatus 503, the sheets serially taken in the above-described manner, aligned into the form of the sheet set by being serially stacked over a processing tray 509 disposed substantially in a horizontal direction with a predetermined tilt. Edges of the sheet set (one corner portion or multiple edge portions) are stapled by a stapling unit 510, and the stapled sheet set is ejected onto a staple tray 511. In a mode of not performing the binding process or the folding process, sheets are ejected and stacked onto a stack tray 512.
However, the sheet processing apparatus 503 is provided on the side face of the mainbody of the image forming apparatus 503, so that the overall apparatus width, that is, the total inclusive of the added width of the sheet processing apparatus is increased, whereby requiring an increased installation occupation area for installation of the overall apparatus.
In addition, a large space in the apparatus height direction is required for the conventional sheet processing apparatus 503 since the saddle tray 504 is formed substantially straight with the steep tilt and is disposed substantially in a vertical direction. Further, since not only that the saddle tray 504 is disposed substantially straight with the sharp angle, but also that the pushing plate 507 operates in the direction substantially perpendicular to the saddle tray 504, whereby causing ineffective use of spacing.
Further, in the conventional sheet processing apparatus 503, the pushing plate 507 performs the folding process, and the processing tray 509 performs the single-side binding process. Thus, the configuration is such that the processes are performed by the different processing trays, therefore requiring corresponding spacing and costs.
Further, in the conventional sheet processing apparatus 503, the pushing plate 507 is formed into the shape of a tray extending in the substantially vertical direction. As such, a large force is required for the pushing plate 507 to fold a sheet set being stacked above the pushing plate 507 to be substantially straight along the substantially vertical direction. This leads to, for example, an increase in the size of a driving source for the pushing plate 507 and an increase in cost.